1. Field of the Invention
This invention relates to the improvement of a carburetor in engines using gasoline, light oil or the like as a fuel for, for example, automobiles,motorcycles and the like.
2. The Background Art
A known structure of such carburetor is, for example, as shown in FIG. 1. Such carburetor is provided with a throttle valve 6 which is moved in the direction crossing with an intake pass 2 in communication with an engine so as to form a variable venturi portion 5 in the intake pass 2. There is a main nozzle 3 for controlling fuel inflow in a manner to cross with the intake pass 2 as with the valve 6. The carburetor is provided with a jet needle 7 which has a taper portion gradually decreasing in diameter toward its head, and whose base end is mounted to said throttle valve, and whose tapering head portion is inserted into the main nozzle 3.
With the axial movement of the throttle valve 6, the gap between the main nozzle 3 and the jet needle 7 is allowed to change, whereby a fuel proportional to the intake flow flowing through the venturi portion is taken in from the main nozzle 3 so as to control the air-fuel ratio.
Known head configurations of the jet needle 7 include a needle configuration in which its body tapers toward its head at a certain taper angle, and a conical configuration in which its body becomes conical at its head.
A main jet 13 is threadingly connected to the lower end of the main nozzle 3. The bottom of the main jet is flat with a single hole therein, and is orthogonal to the outside walls.
A carburator assembly 1 is formed with an intake pass 2 communicating with an engine G, and provided on the lower side of the intake pass 2 is a main nozzle 3 communicating with the intake pass 2. Formed on the upper side of the intake pass 2 is a throttle mechanism 4, and provided slidably in the throttle mechanism 4 is a throttle valve 6 which is moved in the direction crossing with the intake pass 2 so as to form a variable venturi portion 5 in the intake pass 2.
Mounted on the lower end of the throttle valve 6 is a jet needle valve 7, and connected threadingly to the head of the jet needle valve 7 is a main jet 13. The throttle valve 6 is urged by a spring 8, so that the movement of the valve can be adjusted by a throttle lever (not shown).
Formed on the lower side of the intake pass 2 is a fuel tank 9, into which a fuel is supplied through a fuel supply port 10. Provided in the fuel tank 9 is a float 11, and the fuel supply into the fuel tank 9 is controlled by a control valve 12 connected to the float 11. Arrows A, E and F indicate the flow of intake air,mixed gas and fuel, respectively. The fuel sucked by a negative pressure, occurring by the intake air A flowing from an upstream side P1 to a downstream side P2 of the intake pass 2, is first roughly measured by the main jet 13.